Self-drilling and sealing rivet

ABSTRACT

A mandrel-rivet of the pull-to-set type comprises an mandrel head either adapted, or not adapted, to form the installation hole by rotation relative to a workpiece, and its mandrel stem and/or the barrel portion of the rivet are of a configuration to provide space for holding a dormant sealant or adhesive. Rotation of the mandrel relative to the rivet after drilling may provide a melting or curing heat, and subsequent retraction of the mandrel head for rivet setting simultaneously squeezes the sealant through holes in the rivet barrel into the interface region of the joint to provide greater strength and a water-tight seal. A particularly desirable variant contemplates inclusion of a twopart epoxy initially retained in the barrel and divided by the shape of the mandrel section, for instance oval, until the mandrel rotation relative to the rivet will mix the epoxy whereupon the mandrel retraction secures the rivet while exuding activated adhesive for sealing its joint. A drilling-pulling mandrel stem optionally useful in the fastener for attaining so-called flush break joints would be formed with multiple indentations which, though not likely to cause the stem to break under rotary drilling or straight pulling, would cause its rupture where desired when subjected by the installing tool, after rivet setting, to the tensile stress of the pulling and additionally to a tilting of the stem.

United States Patent [1 1 Newton SELF-DRILLING AND SEALING RIVE'I [75]Inventor: Albert E. Newton, Beverly, Mass.

[52] U.S. Cl. 85/68, 85/77, 85/66, 151/ 14.5 [51] Int. Cl. Fl6b 13/06[58] Field of Search 85/63, 66,- 68, 70, 85/71, 72, 77, 78, 1 JP;151/14.5, 41.7

[56] References Cited UNITED STATES PATENTS 1,487,290 3/ 1924 Tomkinson85/66 2,287,395 6/1942 Reynolds 85/66 3,232,162 2/1966 Ketchum 85/773,308,585 3/1967 Fischer 85/63 3,403,593 10/1968 Moore 85/68 3,464,4729/1969 Reynolds... 151/2 R 3,472,301 10/1969 Pearce 85/66 FOREIGNPATENTS OR APPLICATIONS 442,832 2/1936 Great Britain 85/66 PrimaryExaminerMarion Parsons, Jr. Attorney-Carl E. Johnson et a1.

[57] ABSTRACT A mandrel-rivet of the pull-to-set type comprises an Nov.20, 1973 mandrel head either adapted, or not adapted, to form theinstallation hole by rotation relative to a workpiece, and its mandrelstem and/or the barrel portion of the rivet are of a configuration toprovide space for holding a dormant sealant or adhesive. Rotation of themandrel relative to the rivet after drilling may provide a melting orcuring heat, and subsequent retraction of the mandrel head for rivetsetting simultaneously squeezes the sealant through holes in the rivetbarrel into the interface region of the joint to provide greaterstrength and a water-tight sea]. A particularly desirable variantcontemplates inclusion of a two-part epoxy initially retained in thebarrel and divided by the shape of the mandrel section, for instanceoval, until the mandrel rotation relative to the rivet will mix theepoxy whereupon the mandrel retraction secures the rivet while exudingactivated adhesive for sealing its joint.

A drilling-pulling mandrel stem optionally useful in the fastener forattaining so-called flush break joints would be formed with multipleindentations which, though not likely to cause the stem to break underrotary drilling or straight pulling, would cause its rupture wheredesired when subjected by the installing tool, after rivet setting, tothe tensile stress of the pulling and additionally to a tilting of thestem.

2 Claims, 9 Drawing Figures SELF-DRILLING AND SEALING RIVET BACKGROUNDOF THE INVENTION U.S. Pat. No. 3,512,224 issued May 19, I970, upon anapplication filed in my name, discloses a two-part grommet, one part ofwhich has an orifice to allow expulsion of adhesive for bonding thegrommet upon setting the assembly in a structure.

The present invention relates to blind fasteners of the pull-to-settype. More especially this invention pertains to novel mandrel-rivetsadapted both to drill the holes into which they are to be installed andto release and apply, during their installation, a sealant or adhesivecontained in the respective rivet barrels whereby strong, sealed jointsare produced. Tools suitable for blind riveting and for mandrel drillinghave hitherto been known; also, self-drilling mandrel rivets havehitherto been disclosed. So far as I am aware, however, noself-drilling, self-sealing blind fastener has previously beenavailable, and hencethe marked advantages of combining in one fastenerits own hole-making means and joint sealant activation have not hithertobeen-attained.

SUMMARY OF THE INVENTION In view of the foregoing it is a primary objectof this invention to provide an improved pull-to-set fastenerincorporating its own joint sealant exudable upon fastener installation.

Another object of the invention is to provide an improved mandrel-rivethaving the dual capabilities of forming its own mounting hole in astructure, and then, upon relative setting movement of the mandrel andthe rivet, exuding adhesive to produce a fluid-tight joint.

To these ends, and in accordance with a feature of the invention, theconfiguration of a mandrel shank portion and/or the surrounding rivetbarrel portion provide storage for an exudable sealant. In one variant aself-drilling mandrel rivet has a mandrel head swedged to form a drilltip, and that portion of the mandrel stem within the rivet barrel isreduced to enable an adhesive or sealant to be accommodated therein. Thesealant may be of a one-part" type that will become thermoplastic underthe heat and/or squeezing forces generated during the installation, orwhich would cure upon the exclusion of air by formation of the rivetjoint. Alternatively, the sealant may be of the two-part epoxy type. Inthe latter case the mandrel stem within the barrel defines predeterminedstorage volumes for the resin and its activator, holding them separatelyuntil the hole forming, whereupon their admixture is effected byrelative rotation of the rivet and the drilling mandrel, and theadhesive mixture is caused to be exuded for sealing by the relativemandrel retraction to axially compress and set the rivet.

It will be understood that, although the variant form of the novelfastener employing a self-drilling mandrel head is presently preferred,the invention is not necessarily thus limited but may well also residein a pull-toset mandrel rivet initially insertable into a preformed holeand having a non-drilling mandrel head, and a reduced mandrel shankwhich may relatively rotate and or be simply relatively retractive toexude a sealant retained within the unset rivet barrel.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other feature of theinvention will now be more particularly described in connection with anillustrative embodiment, and with reference to the accompanying drawingsthereof, in which:

FIG. 1 is a view in side elevation of a self-drilling mandrel having areduced shank portion formed to accommodate an adhesive;

FIG. 2 is a view similar to FIG. 1 but having its shank portion of ovalcross section;

FIG. 3 is a view in side elevation of a self-drilling rivet-mandrel, theshank of which is cylindrical and formed with flush break grooves;

FIG. 4 is a view in side elevation of a'tubular rivet having sealantorifices and assemblable with either of the mandrels of FIGS. 1-3;

FIG. 5 is a transverse section taken on the line VV of FIG. 7;

FIG. 6 is a transverse section taken on the line VIVI of FIG. 8;

FIG. 7 is a view in side elevation showing the beginning of installationby a tool of a mandrel-rivet including, for example, the mandrel of FIG.2 and a two-part epoxy shown in FIG. 5;

FIG. 8 is a longitudinal section showing the mandrel of FIG. 3 assembledon a rivet having an enlarged bore portion providing a chamber or pocketfor an adhesive deposit, the mandrel having bored a mounting hole byoperation of a tool which is starting mandrel retraction to set therivet; and

FIG. 9 is a longitudinal section showing the mandrelrivet of FIG. 8after installation is completed.

DESCRIPTION OF PREFERRED EMBODIMENTS The following description will bepredicated on the assumption that the self-drilling mandrel is employedin the several mandrel assemblages to be explained by way ofillustration. It will be understood, however, that where the structurein which the fastener is to be secured already has been provided with anappropriate receiving hole, and the heat due to drilling is not requiredfor conditioning of the adhesive, the mandrel may merely have aconventional enlarged head devoid of drilling configurations butemploying one or another of the other novel features associated with themandrel shank as will hereinafter be described.

In FIG. 1 a self-drilling mandrel generally designated 10 has anelongated shank 12 provided with a pulling end 14 (which may be formedwith a gripping means such as grooves not shown), and an oppositeextremity having an enlarged head 16 with a drilling configurationadapted to bore a receiving hole for a tubular rivet barrel 18 (FIG. 4)in a structure S (FIGS. 7-9). It will be understood that the mandrel 10will telescopically receive the rivet barrel 18 as shown in FIG. 7, apreformed flanged end 20 of the rivet being remote from the head 16 andadapted to engage the structure S when in abutting relation with ananvil or nosepiece 22 (FIGS. 7 and 8) of an installing tool. The latter,when the self-drilling head 16 is employed, is of a type adapted torotate the mandrel 10 about its axis and relatively to both thestructure S and the inserted rivet held against rotation by thenosepiece 22, and thereafter axially retract the mandrel relative to therivet as will be described.

In accordance with this invention either a portion of the mandrel shank12 and/or the rivet barrel 18 have a configuration to providetherebetween a space or pocket for the storage of a deposit of adhesiveor sealant 24. This may be a thermoplastic or thermoset type of adhesivewhich would be heatable to fluid state by the friction generated duringrotation of the mandrel within the rivet. For annularly accommodatingthe deposit 24 the mandrel shank 12 is of reduced section as shown at 26(FIG. 1) and axially spaced to communicate, during rivet upsetting, withat least one radial aperture 28 formed in the barrel 18. It will beunderstood that, as indicated in FIGS. 8 and 9, the axial position ofthe barrel apertures 28 preferably corresponds with interfaces of thestructure S in which the fastener assembly is to be secured and to whichthe adhesive or sealant is to be exuded.

In FIG. 2 a self-drilling mandrel generally designated 30 differs fromthat shown in FIG. 1 in that its shank has a reduced portion 32 which isoval in cross section, the major axis diameter correspondingsubstantially to the internal diameter of the barrel 18. In this way, asindicated in FIG. 5, two substantially equal pockets are provided forthe reception and storage of a two-part epoxy 34-36. The resin componentand its activator are kept apart in the fastener assembly until themandrel is relatively rotated during drilling of the installation hole,when mixing of the epoxy will occur, and relative mandrel retractionthereafter to set the rivet forces the mixture through the orifices 28.Thus crevices and voids in the joint, barrel and mandrel are filled toprovide a water-tight, high temperature resistant sea]. It will beappreciated that the mandrel temperature may appropriately rise duringthe drilling, due to heat generated at the drill tip and by reason ofhigh speed rotation of the mandrel, and the heat transmitted byconduction can decrease viscosity of the epoxy and accelerate curing.Also, if desired the nosepiece 22 may itself be heated by means notillustrated.

The mandrels of FIGS. 1 and 2 may, but need not, employ so called flushbreak grooves of the type shown at 40 at FIGS. 2 and 3. The mandrel 42of FIGS. 3, 8, and 9 next to be described is unlike those of FIGS. 1 and2 in that it has no reduced shank portion for accommodating an adhesivedeposit, but is formed with the peripheral grooves 40, or closelyarranged indentations (as in knurling) providing a locality of stressconcentration. The grooves 40, nicks, or indentations do not weaken themandrel to the extent that it breaks during rotation or straightretractive pulling to set the rivet, but they do produce a localizedstress in the mandrel such that, whn the tool not only is exertingretractive pulling stress but is also tilted after tlie rivet has beenset, the mandrel will, due to tensile and bending stress break off atthe desired point, usually even with the rivet flange end as shown inFIG. 9.

The mandrel 42 is especially adapted for use with a tubular rivet 44(FIGS. 8 and 9) which differs from that shown in FIG. 4 in that anenlarged bore portion 46 of the barrel is adapted to retain adhesive orsealant 48 (FIGS. 6, 8 and 9) until at least partly squeezed out oforifice 50 during rivet setting by relative mandrel retraction.

Though not herein illustrated, it will be understood that a two-partepoxy may be employed in the rivet 44, a mandrel of the type shown inFIG. 2 then being employed and having, at its ovalized shank section, amajor axis substantially equal to the internal diameter of the enlargedbore 46.

Installation of the self-drilling and sealing rivet will now be brieflyreviewed, the procedure being essentially the same for any of theseveral combinations mentioned. With the rivet telescoped on one of themandrels in the manner shown in FIG. 7, the installing tool will (bymechanism not herein shown) grip the mandrel with the nosepiece 22bearing on the rivet flange'20. The mandrel is then rotated by the tool,when positioned by the operator, to cause the drilling head 16 to bore ahole in the structure S for receiving the barrel 18. With the nosepiece22 holding the rivet flange in structure-abutting relation and thuspreventing rivet rotation, the relative mandrel rotation heats and/ormixes the adhesive. Next the operator causes the tool to retract thehead 16 for setting the rivet. The blind end of the rivet barrel isaccordingly radially expanded by the head 16, and the adhesive orsealant entrappd between the rivet barrel and the mandrel is exudedthrough the aperture 28 or 50 to tightly seal the rivet joint.

If the installed rivet had a flush break groove 40 or equivalent stressconcentration locality in its mandrel shank the tool would now be tiltedto add a bending stress to the pulling stress on the mandrel whereby itis broken off where desired. The installed rivet thus remains plugged aswell as sealed. A strong joint is afforded by the novel blind fastenerwhich can be quickly and conveniently completed.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

l. A pull-to-set mandrel-rivet comprising, in telescoping relation, atubular rivet having a barrel formed with a flange on one end and aradial orifice spaced therefrom, a mandrel provided with a head remotefrom the flange and having a shank extending through the barrel, thatportion of the shank within the barrel having a roughly oval crosssection to provide two storage spaces bounded by the inner wall of thebarrel, and an epoxy resin and its activator respectively occupying saidspaces, said orifice enabling the resin and the activator, upon relativeupsetting movement of the mandrel and rivet, to flow and mix to form asealant for the rivet.

2. A mandrel-rivet as in claim 1 wherein the mandrel is formed with adrill tip, and operation of the drill tip in forming a work hole for thereception of the mandrel-rivet facilitates the subsequent admixture ofthe resin and its activator by supplying heat due to friction. =0:

1. A pull-to-set mandrel-rivet comprising, in telescoping relation, atubular rivet having a barrel formed with a flange on one end and aradial orifice spaced therefrom, a mandrel provided with a head remotefrom the flange and having a shank extending through the barrel, thatportion of the shank within the barrel having a roughly oval crosssection to provide two storage spaces bounded by the inner wall of thebarrel, and an epoxy resin and its activator respectively occupying saidspaces, said orifice enabling the resin and the activator, upon relativeupsetting movement of the mandrel and rivet, to flow and mix to form asealant for the rivet.
 2. A mandrel-rivet as in claim 1 wherein themandrel is formed with a drill tip, and operation of the drill tip informing a work hole for the reception of the mandrel-rivet facilitatesthe subsequent admixture of the resin and its activator by supplyingheat due to friction.